Tissue adhesives and sealants have many potential medical applications, including wound closure, supplementing or replacing sutures or staples in internal surgical procedures, preventing leakage of fluids such as blood, bile, gastrointestinal fluid and cerebrospinal fluid, adhesion of synthetic onlays or inlays to the cornea, drug delivery devices, and as anti-adhesion barriers to prevent post-surgical adhesions. Conventional tissue adhesives are generally not suitable for a wide range of adhesive applications. For example, cyanoacrylate-based adhesives have been used for topical wound closure, but the release of toxic degradation products limits their use for internal applications. Fibrin-based adhesives are slow curing, have poor mechanical strength, and pose a risk of viral infection. Additionally, fibrin-based adhesives do not bond covalently to the underlying tissue.
Several types of hydrogel tissue adhesives have been developed, which have improved adhesive and cohesive properties and are nontoxic. These hydrogels are generally formed by reacting a component having nucleophilic groups with a component having electrophilic groups that are capable of reacting with the nucleophilic groups of the first component, to form a crosslinked network via covalent bonding. A number of these hydrogel tissue adhesives are prepared using an oxidized polysaccharide containing aldehyde groups as one of the reactive components (see for example, Kodokian et al., copending and commonly owned U.S. Patent Application Publication No. 2006/0078536, Goldmann, U.S. Patent Application Publication No. 2005/0002893, and Nakajima et al., U.S. Patent Application Publication No. 2008/0319101). However, the instability of oxidized polysaccharides in aqueous solution limits their shelf-life for commercial use.
Gallant et al. (Reactive Polymers, Ion Exchangers, Sorbents 8(2):129-136, 1988) describes soluble dextran derivatives containing aldehyde side groups that are prepared by reacting a 4-nitrophenyl carbonate ester of dextran with 2,3-dihydroxypropylamine and subsequent selective periodate oxidation of the pendant diol groups. However, the resulting dextran aldehydes were unstable when heated in mildly acidic media, undergoing aldol reactions.
Therefore, the need exists for polysaccharides containing aldehyde groups, which are more stable in aqueous solution than oxidized polysaccharides, for use in forming hydrogel tissue adhesives and sealants for medical use.